1. Technical Field
The present disclosure relates to dimming systems or dimmer switches, and, in particular, to a dimming system or dimmer switch powered by two current sources. Additionally, the present disclosure relates to a dimming system or dimmer switch having an operation indicator module for indicating at least one operating condition. Further, the present disclosure relates to a method for connecting the dimming system to a load and the two current sources, which includes an alternative return path (e.g., an earth ground), for powering the dimming system.
2. Description of Related Art
Many countries have an electric grid infrastructure that uses alternating current as a power source (referred to herein as an “AC source”). These systems can be either balanced or unbalanced and may include one or more phases, e.g., a three-phase AC source may include a first line that provides a zero phase AC source, a second line that provides a 120-degree phase AC source, a third line that provides a 240-degree phase AC source, and a return path (usually referred to as a “neutral” line). The “neutral” line can be used as a return path for the AC source supplied by the first, second, and third lines. A line is a conductive path that can also be referred to as a “wire”. The terms “line”, “conductive line”, and “wire” are considered herein to be synonymous.
However, many AC wiring systems (e.g., those found in typical dwellings) also utilize an alternative return path called an earth ground. The earth ground, sometimes confusingly referred to simply as “the ground,” is generally used as a safety feature by providing an alternative return path to the return path provided by the neutral line. The earth ground may be formed by several conductive rods that are sufficiently driven into the earth. A sufficient number of rods of sufficient length are used to provide a high current capacity conductive connection to the earth with relatively low impedance.
To illustrate the advantages of using an electric wiring system that uses an earth ground, consider the following: consider a line that provides an AC source (i.e. a “hot” line) that becomes damaged and/or dislodged, thus touching the metal housing of an AC outlet. The AC outlet may become electrified, or “hot”. Any person that touches the metal housing of the AC outlet may form a complete circuit from the AC source through that person's body to the earth (the earth is for all practical purposes an infinite electron source and an infinite electron sink). To prevent this from occurring, the metal housing may be conductively connected to that earth ground, thus effectively forming a wired connection to the earth. With the added safety feature of an earth ground if a “hot” line touches a “grounded” metal housing (such as a metal housing of an AC outlet), the current will increase until a circuit protection device detects the rapid rise in current and interrupts the AC source. Modern electrical systems use circuit breakers that automatically detect unsafe current levels by monitoring the magnetic field created by the AC source and/or by monitoring heat that results from the energy dissipated by the flowing electrons.
Many dwellings and office buildings use either a single-phase, two-phase, or three-phase AC source and/or some combination thereof. The AC source may be accessed by standardized connections (referred to as “plugs”) that prevent a user from improperly connecting to an AC source, e.g., a three-phase AC plug cannot connect to a two-phase AC outlet. Additionally, many AC sources may selectively apply electricity to a load based upon whether a switch is turned on or off, e.g., a light switch.
It is well known how to control the brightness of a light by using a dimming system (or dimming switch) that is connected between a hot line and a load line (the load line connects to the load while the load is also connected to the neutral line, thus forming a complete circuit). These dimming systems are usually powered from current flowing between the hot line to the load via the load line, and consequently through the load and the neutral line. Typical dimming systems do not have a direct connection to the neutral line. This allows a dimming system to be quickly and easily installed as a replacement for a mechanical on/off switch because these dimmer switches do not require an additional wire directly connected to the neutral line.
Because the two-line dimming system controls the power dissipation of the load by utilizing a TRIAC, SCRs, MOSFETs, JGBTs and the like power switches, the dimming system turns off these power switches at a small portion of every half cycle of an AC source and uses this time to charge the power supply to power its various components. The human eye does not see or perceive these interruptions of power to the load.
There are at least two drawbacks associated with the prior art two-line dimming systems. First, since the load affects how much power can be provided to the dimming system, two-line dimming systems have a minimum power load requirement. If the load power rating (or maximum power dissipation) is less than the minimum power load requirement (typically less than 25-40 W), the dimming system gets inadequate power to operate causing the dimming system to stop working. Another drawback of two-line dimming systems is that if the load gets burned out the two-line dimming system cannot power itself (e.g., the primary conductive path of the load forms an open circuit).
In both of these two situations, the dimming system's components, including its processor (e.g., microcontroller), cannot be powered up and the dimming system stops operating. Without an adequate power supply (or power source), the dimming system is not capable of providing an indication to the user that the dimming system is operating properly and the problem lies elsewhere. Accordingly, it would be beneficial to the user to know that the two-line dimming system is not broken or malfunctioning. Providing such an indication technique can facilitate a user's determination as to whether the load is burned out or as to whether the load's power rating is too low for the dimming system to operate. This will reduce the amount of service calls and unnecessary replacements of two-line dimming systems or dimming switches.